8297451: ProcessHandleImpl should assert privilege when modifying reaper thread

Reviewed-by: chegar, alanb

src/java.base/share/classes/java/lang/ProcessHandleImpl.java

@@ -100,7 +100,7 @@ final class ProcessHandleImpl implements ProcessHandle {
                 ThreadFactory threadFactory = grimReaper -> {
                     Thread t = InnocuousThread.newSystemThread("process reaper", grimReaper,
                             stackSize, Thread.MAX_PRIORITY);
-                    t.setDaemon(true);
+                    privilegedThreadSetDaemon(t, true);
                     return t;
                 };
 
@@ -115,6 +115,22 @@ final class ProcessHandleImpl implements ProcessHandle {
         }
     }
 
+    @SuppressWarnings("removal")
+    private static void privilegedThreadSetName(Thread thread, String name) {
+        AccessController.doPrivileged((PrivilegedAction<Void>) () -> {
+            thread.setName(name);
+            return null;
+        });
+    }
+
+    @SuppressWarnings("removal")
+    private static void privilegedThreadSetDaemon(Thread thread, boolean on) {
+        AccessController.doPrivileged((PrivilegedAction<Void>) () -> {
+            thread.setDaemon(on);
+            return null;
+        });
+    }
+
     /**
      * Returns a CompletableFuture that completes with process exit status when
      * the process completes.
@@ -140,8 +156,9 @@ final class ProcessHandleImpl implements ProcessHandle {
                 processReaperExecutor.execute(new Runnable() {
                     // Use inner class to avoid lambda stack overhead
                     public void run() {
-                        String threadName = Thread.currentThread().getName();
+                        Thread t = Thread.currentThread();
-                        Thread.currentThread().setName("process reaper (pid " + pid + ")");
+                        String threadName = t.getName();
+                        privilegedThreadSetName(t, "process reaper (pid " + pid + ")");
                         try {
                             int exitValue = waitForProcessExit0(pid, shouldReap);
                             if (exitValue == NOT_A_CHILD) {
@@ -172,7 +189,7 @@ final class ProcessHandleImpl implements ProcessHandle {
                             completions.remove(pid, newCompletion);
                         } finally {
                             // Restore thread name
-                            Thread.currentThread().setName(threadName);
+                            privilegedThreadSetName(t, threadName);
                         }
                     }
                 });

test/jdk/java/lang/ProcessBuilder/SecurityManagerClinit.java

@@ -24,7 +24,7 @@
 
 /*
  * @test
- * @bug 6980747
+ * @bug 6980747 8297451
  * @summary Check that Process-related classes have the proper
  *     doPrivileged blocks, and can be initialized with an adversarial
  *     security manager.
@@ -52,6 +52,17 @@ public class SecurityManagerClinit {
         }
     }
 
+    // Security manager that unconditionally performs Thread Modify Access checks.
+    @SuppressWarnings("removal")
+    private static class TMACSecurityManager extends SecurityManager {
+        static final RuntimePermission MODIFY_THREAD_PERMISSION =
+                new RuntimePermission("modifyThread");
+        @Override
+        public void checkAccess(Thread thread) {
+            checkPermission(MODIFY_THREAD_PERMISSION);
+        }
+    }
+
     public static void main(String[] args) throws Throwable {
         String javaExe =
             System.getProperty("java.home") +
@@ -60,10 +71,11 @@ public class SecurityManagerClinit {
         final SimplePolicy policy =
             new SimplePolicy
             (new FilePermission("<<ALL FILES>>", "execute"),
-             new RuntimePermission("setSecurityManager"));
+             new RuntimePermission("setSecurityManager"),
+             new RuntimePermission("modifyThread"));
         Policy.setPolicy(policy);
 
-        System.setSecurityManager(new SecurityManager());
+        System.setSecurityManager(new TMACSecurityManager());
 
         try {
             String[] cmd = { javaExe, "-version" };